Structure, Spectroscopy and Enhanced 2.8 μm Laser Performance of a High-Entropy Er:GdLuYSGG Crystal

A novel high-entropy laser crystal of 30 at. % Er:GdLuYSGG was grown by the Cz method. The crystal exhibits high crystalline quality, evidenced by an X-ray rocking curve FWHM of 0.007°. The thermal expansion coefficient and thermal conductivity are determined to be 1.52 × 10–5 K–1 and 4.10 W m–1 K–1, respectively. A broadened fluorescence band around 2760–2840 nm is observed and attributed to the lattice distortion effect of the high-entropy crystal, indicating the Er:GdLuYSGG crystal is beneficial for realizing tunable or ultrafast lasers. By a 973 nm LD end-pumping, a continuous-wave 2.8 μm laser is achieved with a maximum output power of 1062 mW, corresponding to a slope efficiency of 17.99%. The Mx2/My2 factors are 1.35 and 1.37, suggesting a high laser beam quality. The results imply that the high-entropy Er:GdLuYSGG crystal is a promising broadband gain medium for high-performance 2.8 μm mid-infrared laser, which might be particularly suited for applications in space radiation environments.